1. Field of the Invention
The present invention relates to a multicore fiber.
2. Description of the Related Art
In recent years, a technique to use a multicore fiber which is an optical fiber having a plurality of cores as a transmission fiber has been suggested. Transmission capacity can be increased by using the multicore fiber compared with the case of using an optical fiber having a single core.
As such a multicore fiber, a fiber having a hole assisted structure in which air holes (sub medium regions) are provided around each core has been known. Japanese Patent Laid-Open No. 2011-18013 (JP-A 2011-18013) shows an example of the hole assisted multicore fibers. According to this multicore fiber, crosstalk between the cores can be reduced by presence of the air holes around each core.